Brendan Abela tried to pay his former partner and her two friends $20,000 in hush money a week after robbing them.
Abela messaged the woman, who had dumped him, offering to pay them all to withdraw their police statements so his charges would be dropped in June 2015.
Court documents show he told her there was no point praying to God as she was the only person who could help him.
The 35-year-old also swore to leave her alone if she complied.
"If they withdraw the statement and make a no complaint statement and you do (then) I'll walk," Abela told the woman, who cannot be named.
"And it's only your statement that the police are charging me on. No one has to know anything just the people involved.
"20 grand withdraw the statements and ... I'll be out your life."
Abela on Tuesday faced the Victorian County Court, where he was sentenced to 18 months in prison for attempting to pervert the course of justice.
He is already behind bars serving an 11-year sentence for a separate conviction and is not eligible for parole until 2028.
But Judge Scott Johns ruled that Abela's fresh sentence would be served alongside his existing one, meaning he won't spend extra time in prison.
He had earlier pleaded guilty to one charge of attempting to pervert the course of justice.
